/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.leaderelection;

import javax.annotation.Nullable;

import java.io.Serializable;
import java.util.Objects;
import java.util.UUID;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * Information about leader including the confirmed leader session id and leader address.
 */
public class LeaderInformation implements Serializable {

	private static final long serialVersionUID = 1L;

	@Nullable
	private final UUID leaderSessionID;

	@Nullable
	private final String leaderAddress;

	private static final LeaderInformation EMPTY = new LeaderInformation(null, null);

	private LeaderInformation(@Nullable UUID leaderSessionID, @Nullable String leaderAddress) {
		this.leaderSessionID = leaderSessionID;
		this.leaderAddress = leaderAddress;
	}

	@Nullable
	public UUID getLeaderSessionID() {
		return leaderSessionID;
	}

	@Nullable
	public String getLeaderAddress() {
		return leaderAddress;
	}

	public boolean isEmpty() {
		return this == EMPTY;
	}

	@Override
	public boolean equals(Object obj) {
		if (obj == this) {
			return true;
		} else if (obj != null && obj.getClass() == LeaderInformation.class) {
			final LeaderInformation that = (LeaderInformation) obj;
			return Objects.equals(this.leaderSessionID, that.leaderSessionID) &&
				Objects.equals(this.leaderAddress, that.leaderAddress);
		} else {
			return false;
		}
	}

	@Override
	public int hashCode() {
		int result = Objects.hashCode(leaderSessionID);
		result = 31 * result + Objects.hashCode(leaderAddress);
		return result;
	}

	public static LeaderInformation known(UUID leaderSessionID, String leaderAddress) {
		return new LeaderInformation(checkNotNull(leaderSessionID), checkNotNull(leaderAddress));
	}

	public static LeaderInformation empty() {
		return EMPTY;
	}

	@Override
	public String toString() {
		return "LeaderInformation{" +
			"leaderSessionID='" + leaderSessionID + '\'' +
			", leaderAddress=" + leaderAddress +
			'}';
	}
}
